Yes, that is the tranny cooling line. The passenger side has a small elbow at the radiator end, spring covered fitting at the fluid line end. When removing, the radiator end you need just 1 19mm wrench, but at the fluid line end make sure you hold the line nut with a 17 mm wrench as you loosen the 19mm fitting. I suggest replacing the driver side as well, which has the spring at both ends, or as I see the replacements have it springed the entire length. You may lose about 1/2 qt of tranny fluid when removing and replacing these lines.

IF you are CERTAIN you are getting antifreeze leaking and NOT tranny fluid, then you have a radiator leak somewhere above your tranny line filtting.